Treatment of synthetic yarns

ABSTRACT

In a method of treating a synthetic yarn, the yarn is advanced over a heat transfer element by the passage of the yarn at one end or at each end of the element over guide means which causes a reversal of the direction of travel of the yarn over the element and a transfer of the yarn from a path in contact with one side of the element to a path in contact with the other side of the element and which is stationarily arranged or arranged in operation to revolve at a speed less than that of the contacting traveling yarn. The yarn upon leaving the element is twisted by twisting means with the twist running back to the yarn passing over the element beyond the guide means or beyond at least the last contacted guide means.

United States Patent 1 Hooper et al.

[54] TREATMENT OF SYNTHETIC YARNS [75] Inventors: Norbert Hooper, Castleton, near Rochdale; Terence Gurnshaw, Accriggton, both of England [73] Assignee: T.M.M. (Research) Limited, Lancashire, England [22] Filed: Dec. 14, 1970 [21] Appl. No.: 97,969

[30] Foreign Application Priority Data Dec. 16, 1969 Great Britain ..61,237l69 [52] US. Cl. ..57/34 HS, 57/51, 57/157 TS [51] Int. Cl. ..D01h 13/28, D02j 13/00 [58] Field of Search .....57/34 R, 34 HS, 36, 51, 77.3,

57/157 R, 157 TS, 157 MS; 28/62 [56] References Cited UNITED STATES PATENTS 3,449,898 6/1969 Fujita et a] ..57/34 HS 1 Apr. 3, 1973 Primary Examiner-Donald E. Watkins Attorney-Watson, Cole, Grindle & Watson [57] ABSTRACT In a method of treating a synthetic yarn, the yarn is advanced over a heat transfer element by the passage of the yarn at one end or at each end of the element over guide means which causes a reversal of the direction of travel of the yarn over the element and a transfer of the yarn from a path in contact with one side of the element to a path in contact with the other side of the element and which is stationarily arranged or arranged in operation to revolve at a speed less than that of the contacting traveling yarn. The yarn upon leaving the element is twisted by twisting means with the twist running back to the yarn passing over the element beyond the guide means or beyond at least the last contacted guide means.

23 Claims, 5 Drawing Figures PATENTEDAFR3 I973 3 724 191 SHEET 1 OF 2 TREATMENT OF SYNTHETIC YARNS The present invention relates to methods of and apparatus for treating synthetic yarns.

It is well known that a synthetic yarn may be advanced over a heating or cooling device whilst twist is being inserted to produce, for instance, crimped synthetic yarn. In false twist crimping operations the need has arisen in recent years for higher processing speeds and in order to raise the temperature of the travelling yarn to the desired level it has been found to be necessary to provide heaters of greater length. This has led to the design of false twist crimping machines which are either very high and not easily attended to by the operative, or which have a complicated yarn path and occupy a lot of floor space.

Attempts have been made to make several passes of the travelling yarn to and fro over a single heater in order to reduce the heater length, but difficulty is experienced as the twist inserted in the yarn does not readily pass beyond the point at which the direction of the yarn path is changed. Attempts to overcome this difiiculty have been made by inserting moving twisting devices at the reversal point, but this has led to additional complication in the design of such machines.

According to a first aspect of the present invention, there is provided apparatus for treating a synthetic yarn comprising a heat transfer element over which the yarn is passed, in contact therewith, twisting means to impart twist to said yarn upon leaving said element, and yarn guide means at one end or at each end of said element over which the yarn is caused to pass and which causes a reversal of the direction of travel of the yarn.

over the heater element and a transfer of the yarn from a path in contact with one side of the element to a path in contact with the other side of the element, said yarn guide means or each of said yarn guide means being stationary or being arranged in operation to revolve at a speed less than that of the contacting travelling yarn, whereby twist imparted to the yarn runs back to the yarn passing over the element beyond the guide means or beyond at least the last contacted guide means.

According to a second aspect of the present invention, there is provided a method of treating a synthetic yarn comprising the steps of advancing said yarn over a heat transfer element by the passage of the yarn at one end or at each end of said element over guide means which causes a reversal of the direction of the travel of the yarn over the element and a transfer of the yarn from a path in contact with one side of the element'to a path in contact with the other side of the element and which is stationarily arranged or arranged in operation to revolve at a speed less than that of the contacting travelling yarn, and using means to impart to said yarn upon leaving the element a twist which runs back to the yarn passing over the element beyond the guide means or beyond at least the last-contacted guide means.

Some embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which:

FIG. 1 is a schematic front elevation of crimping apparatus according to a first embodiment of the invention,

FIG. 2 is a side elevation of part of the apparatus shown in FIG. 1

FIG. 3 is a schematic side elevation of part of a yarn crimping apparatus according to a second embodiment of the invention,

FIG. 4 is a schematic front elevation of crimping ap paratus according to a third embodiment of the invention, with parts thereof shown in section, and

FIG. 5 is a side elevation of the apparatus shown in FIG. 4.

Referring first to FIGS. 1 and 2, a continuous filament yarn Y of synthetic material is forwrde'd by feed rollers 1 and 2 to a heater 3 over one side of which the yarn passes downwardly to a stationary guide pin 4, round which the yarn passes in a circumferential groove formed in the pin. From the pin 4, the yarn is passed in contact with the other side of the heater 3 upwardly to a stationary guide pin 5 round which the yarn passes in a circumferential groove formed in the pin. The yarn then again passes in contact with the said one side of the heater 3 and on leaving the latter passes through a false-twisting device 6, from which it is taken-up by delivery rollers 7 and 8. The device 6 may be a friction twister of the bush type, as shown, or any of the known rotating false twist tubes. It will be seen that the circumferential grooves provided in the guide pins 4 and 5 serve to hold the yarn in spaced paths during its traverse over the heater 3. Between the ends of the heater 3 and the associated guide pins 4 and 5 there are arranged driven rollers 9 and 10 which assist in the advancement of the yarn over the surface of the heater 3.

In operation, the twist inserted by the false-twisting device 6 runs back into the heating zone provided by the heater 3 and it has been found that contrary to what was previously believed the twist runs past the guide pins 4, 5 provided that the path of yarn contact with the guide pins 4, 5 is not too long and that the pins 4, 5 are held stationary or allowed to rotate at a speed less than the speed of the contacting yarn. If the guide pin 5 is caused to rotate at the speed of the yarn, the passage of twist over the pin is hindered.

It will be appreciated that the effective heating of the yarn by the heater 3 can be varied to suit the processing conditions required by varying the number of passes which the yarn makes over the heater 3.

In the embodiment of the invention illustrated in FIG. 3, the yarn Y is guided over the two sides of the heater 3 by guide pins 4 and 5 and twist is imparted to the yarn in the same manner by a false-twisting device 6. The driven rollers 9 and 10 are however replaced by freely rotating pairs of rollers 11, 11' and 12, 12 which serve to prevent the yarn from fouling the edges of the heater.

In a further embodiment of the invention (not shown) a very narrow double sided heater may be used having grooved guides immediately adjacent each end of the heater to provide the required reversing of the yarn path and the separation of them over the heater.

Satisfactory crimping can be achieved when stationary guides are used, butwith certain types of yarn or guide surfaces there is the risk of spin finish accumulating on the guides and to prevent this it may be found desirable to allow the guide'to rotate against a braking action or to drive the guide, but in either case it is important that the speed of the guide should not approach or equal the speed of the yarn contacting it. As the movement imparted to the guide will be in the same direction as yarn travel no transverse twisting movement will be exerted on the yarn.

It will be appreciated that in addition to allowing twist to pass through heating zones the invention will allow twisted yarns to be passed through heating and/or cooling zones.

Referring now to FIGS. 4 and 5, a continuous undrawn filament yarn Y of 20 denier nylon 6 is fed by rollers (not shown) to a draw pin 13 around which the yarn is wrapped once, whereafter it is wrapped around a draw roller assembly 14' situated about three feet away from the pin 13, thus creating a draw zone between the draw pin 13 and the draw assembly 14. The latter consists of a driven draw roller 15 and a separator 16 to produce the required number of wraps. A rubber cott roller 17 is spring-loaded against the draw roller 15 to nip the final yarn wrap for a purpose which will hereinafter be described. The draw ratio is 3.2 to l.

The drawn yarn Y passes at a speed of about 500 m.p.mt from the draw roller 15 to the heater 3, which is 600 mm. long, and over one side thereof downwardly to a guide pin 4 round which the yarn passes in a circumferential groove formed in the pin. The pin 4 is driven at about rpm. from a pulley 18 engaged by a driving belt 181. From the guide pin 4 the yarn passes in contact with the other side of the heater 3 which is maintained at about 183 C and then upwardly to a guide pin 5 which is also driven by the belt 181 at about 5 r.p.m., and around which the yarn passes in a circumferential groove formed in the pin. The pins 4 and 5 are driven at 5 rpm. in the direction of the contacting travelling yarn Y.

The yarn Y then again passes in contact with said one side of the heater 3 and on leaving the latter passes at an angle of about 85 through the entrance of a first twisting bush 19 situated 70 cm. from the heater. The yarn passes through the first bush 19 diagonally and leaves it to enter a second bush 20 in series with the first bush. The yarn Y takes a diagonal path through the second bush 20 and leaves it at an exit angle of about 65.

Each of the bushes I9 and 20 is mounted in highspeed bearings (not shown) and the bushes are driven by a common belt 21 in opposite directions, which mutually assists in imparting false twist to the yarn Y running through them due to the reversed yarn path. The bushes 19 and 20 consist'of steel cylinders 191 and 201 with insert rings 192, 193 and 202, 203 of polyurethane. The rings areof quadrant-section presenting an outwardly flared entrance and exit for the yarn.

The yarn Y, on leaving'the bush 20, then passes through the nip of a pair of delivery rollers 7 and 8 which advance the yarn over the heater 3 and through the bushes 19 and 20 at the same rate as that at which it is delivered by the draw rollers and 16, that is to say, without intentional underfeed or overfeed. Thus, the yarn Y is drawn to the optimum ratio entirely in the draw zone. The twist imparted to the yarn at the bushes 19 and runs back over the heater 3 as far as the nip between the draw roller 14 and the'rubber cott roller 17, but is prevented from entering'the draw zone by the cott roller 17. Twist does not normally run forwardly of the twisting bushes l9 and 20 because the twist imparted is not true twist. However, irregularities in the yarn occasionally cause momentary twisting of the yarn in advance of the bush 20, but this can be prevented from running further forward by a snubbing pin.

v yarn Y. Furthermore, if desired, the yarn Y may be advanced over the heater 3 to the delivery rollers 7 and 8 with up to 7 percent underfeed or with up to 7 percent overfeed.

' Crimping apparatus according to the invention permits the use of a short heater and the apparatus may therefore be made very compact. The period for which the yarn remains in contact with the heater is even at high speeds, long enough to heat the yarn sufficiently and the apparatus can therefore be used for treating heavy denier yarn where there is more yarn per unit length to heat up. Yarns from 1S-200 denier can be texturized by the apparatus described in the third embodiment. Furthermore, higher throughputs of yarn are acceptable particularly with the crimping apparatus hereinbefore described with reference to FIGS. 4 and 5, which utilizes a pair of false twist bushes in series for imparting twist to the yarn. The second bush in this embodiment puts in less twist than the first bush and in practice the throughput rates are determined by the rate at which twist can be inserted. Although theoretically, an arrangement including a third bush would be better than the two bush arrangement one may encounter diminishing returns.

What we claim as our invention and desire to secure by Letters Patent is:

l. A method of treating a synthetic yarn comprising the steps of advancing said yarn over a heat transfer element, reversing the direction of travel of the yarn over the element with guide means and transferring the yarn from a path in contact with one side of the element to a path in contact with the other side of the element, maintaining the linear speed of advancement of the yarn at a rate which is relatively-greater than the linear speed of the portions of the glide means which are in instantaneous contact with the travelling yarn, and then imparting-to said yarn, as it leaves the element, twist which runs back to the yarn passing over the element beyond at least the last contacted guide means.

2. A method as claimed in claim 1 wherein the twist imparted is false twist.

3. A method as claimed in claim 1 and further com- I prising assisting the advancement of the yarn to the 5. A method as claimed in claim 1 and further comprising the step of fully drawing the yarn before advancing the yarn over the heat transfer element.

6. A method as claimed in claim 5 wherein the yarn is overfed by up to 7 percent over the heat transfer element to driven delivery rollers situated beyond the twisting means.

7. A method as claimed in claim 1 and further comprising the step of partially drawing the yarn to meet a predetermined minimum draw ratio requirement before advancing the yarn over the heat transfer element.

8. A method as claimed in claim 7 wherein the partial drawing of the yarn is performed by underfeeding the yarn by up to 7 percent over the heat transfer element to driven delivery rollers situated beyond the twisting means.

9. A method as claimed in claim 1 further comprising the step of preventing twist from running forwardly of the twisting means by situating a peg beyond the twisting means and wrapping the yarn around the peg.

10. A method as claimed in claim 1 wherein the yarn is a polyester yarn such as polyethylene terephthalate or a polyamide such as nylon.

1 1. A method of treating a synthetic yarn as set forth in claim 1 wherein the guide means are stationary.

12. A method as set forth in claim 1 wherein is included the step of rotating said guide means at a rate to provide a linear speed at the portions thereof in instantaneous contact with the yarn which is relatively less than the forward linear speed of the yarn.

13. A method as set forth in claim 1- wherein is included the step of rotating said guide means in a direction counter to the direction of advancement -of the yarn.

14. Apparatus for treating a synthetic yarn comprising a heat transfer element over which the yarn is passed in contact therewith, twisting means arranged to impart twist to said yarn upon leaving said element and yarn guide means at at least one end of said element over which the yarn is caused to pass and which causes a reversal of the direction of travel of the yarn over the heat element and the transfer of the yarn from a path in contact with one side of the element to a path in contact with the other side of the element, means for advancing the yarn over said guide means at a linear speed of advancement which is relativelygreater than the linear speed of the portions of said yarn guide means which are in instantaneous contact with the travelling yarn, whereby twist imparted to the yarn runs drivable roller is situated between at least one guide means and an adjacent end of the element for assisting the movement of the yarn over the heat transfer element.

16. Apparatus as claimed in claim 14 wherein said twisting means comprises a rotary false twist bush for imparting false twist to the yarn passing therethrough.

17. Apparatus as claimed in claim 14 wherein said twisting means comprises a pair of rotary false twist bushes for successively imparting false twist to the yarn which passes first to one of the bushes and then to the other.

18. Apparatus as claimed in claim 14 and further comprising yarn drawing means for drawing the yarn before it passes the heat transfer element.

19. Apparatus as claimed in claim 18 wherein the yarn drawing means comprises a draw roller assembly around which the yarn forms a plurality of wraps and a nip roller which cooperates with the draw roller assembly to nip one of the yarn wraps and prevents twist in the yarn running back to the draw zone.

20. Apparatus as claimed in claim 14 and further comprising a snubbing pin engaged by the yarn after leaving the twisting means for preventing twist running forwardly of the snubbing pin.

21. Apparatus for treating synthetic yarn as set forth in claim 14 wherein said guide means are stationary.

22. Apparatus as set forth in claim 14 wherein said guide means are rotatable, there being included means for rotating the guide means at a rate to provide a linear speed at the portions thereof in instantaneous contact with the yarn which is relatively less than the forward linear speed of the yarn.

23. Apparatus as set forth in claim 14 wherein said guide means are rotatable, there being included means for rotating the guide means in a direction counter to the direction of advancement of the yarn. 

1. A method of treating a synthetic yarn comprising the steps of advancing said yarn over a heat transfer element, reversing the direction of travel of the yarn over the element with guide means and transferring the yarn from a path in contact with one side of the element to a path in contact with the other side of the element, maintaining the linear speed of advancement of the yarn at a rate which is relatively greater than the linear speed of the portions of the guide means which are in instantaneous contact with the travelling yarn, and then imparting to said yarn, as it leaves the element, twist which runs back to the yarn passing over the element beyond at least the last contacted guide means.
 2. A method as claimed in claim 1 wherein the twist imparted is false twist.
 3. A method as claimed in claim 1 and further comprising assisting the advancement of the yarn to the heat transfer element by a driven roller situated between at least one guide means and an adjacent end of the element.
 4. A method as claimed in claim 3 further comprising the step of passing the yarn in contact successively with said one side of the heat transfer element, the said other side of the heat transfer element and then said one side of the transfer element again.
 5. A method as claimed in claim 1 and further comprising the step of fully drawing the yarn before advancing the yarn over the heat transfer element.
 6. A method as claimed in claim 5 wherein the yarn is overfed by up to 7 percent over the heat transfer element to driven delivery rollers situated beyond the twisting means.
 7. A method as claimed in claim 1 and further comprising the step of partially drawing the yarn to meet a predetermined minimum draw ratio requirement before advancing the yarn over the heat transfer element.
 8. A method as claimed in claim 7 wherein the partial drawing of the yarn is performed by underfeeding the yarn by up to 7 percent over the heat transfer element to driven delivery rollers situated beyond the twisting means.
 9. A method as claimed in claim 1 further comprising the step of preventing twist from running forwardly of the twisting means by situating a peg beyond the twisting means and wrapping the yarn around the peg.
 10. A method as claimed in claim 1 wherein the yarn is a polyester yarn such as polyethylene terephthalate or a polyamide such as nylon.
 11. A method of treating a synthetic yarn as set forth in claim 1 wherein the guide means are stationary.
 12. A method as set forth in claim 1 wherein is included the step of rotating said guide means at a rate to provide a linear speed at the portions thereOf in instantaneous contact with the yarn which is relatively less than the forward linear speed of the yarn.
 13. A method as set forth in claim 1 wherein is included the step of rotating said guide means in a direction counter to the direction of advancement of the yarn.
 14. Apparatus for treating a synthetic yarn comprising a heat transfer element over which the yarn is passed in contact therewith, twisting means arranged to impart twist to said yarn upon leaving said element and yarn guide means at at least one end of said element over which the yarn is caused to pass and which causes a reversal of the direction of travel of the yarn over the heat element and the transfer of the yarn from a path in contact with one side of the element to a path in contact with the other side of the element, means for advancing the yarn over said guide means at a linear speed of advancement which is relatively greater than the linear speed of the portions of said yarn guide means which are in instantaneous contact with the travelling yarn, whereby twist imparted to the yarn runs back along the yarn passing over the element beyond at least the last contacted guide means.
 15. Apparatus as claimed in claim 14 wherein a drivable roller is situated between at least one guide means and an adjacent end of the element for assisting the movement of the yarn over the heat transfer element.
 16. Apparatus as claimed in claim 14 wherein said twisting means comprises a rotary false twist bush for imparting false twist to the yarn passing therethrough.
 17. Apparatus as claimed in claim 14 wherein said twisting means comprises a pair of rotary false twist bushes for successively imparting false twist to the yarn which passes first to one of the bushes and then to the other.
 18. Apparatus as claimed in claim 14 and further comprising yarn drawing means for drawing the yarn before it passes the heat transfer element.
 19. Apparatus as claimed in claim 18 wherein the yarn drawing means comprises a draw roller assembly around which the yarn forms a plurality of wraps and a nip roller which cooperates with the draw roller assembly to nip one of the yarn wraps and prevents twist in the yarn running back to the draw zone.
 20. Apparatus as claimed in claim 14 and further comprising a snubbing pin engaged by the yarn after leaving the twisting means for preventing twist running forwardly of the snubbing pin.
 21. Apparatus for treating synthetic yarn as set forth in claim 14 wherein said guide means are stationary.
 22. Apparatus as set forth in claim 14 wherein said guide means are rotatable, there being included means for rotating the guide means at a rate to provide a linear speed at the portions thereof in instantaneous contact with the yarn which is relatively less than the forward linear speed of the yarn.
 23. Apparatus as set forth in claim 14 wherein said guide means are rotatable, there being included means for rotating the guide means in a direction counter to the direction of advancement of the yarn. 